For subjective evaluation, we invite 5 participants with professional knowledge in music and singing as human annotators to evaluate 10 songs (338 pairs of generated lyric sentences and melody phrases) randomly selected from our test set. We require each annotator to answer some questions using a five-point scale, from 1 (Poor) to 5 (Perfect). The whole evaluation is conducted in a blind-review mode. Inspired by [1]}, the metrics to evaluate the generated lyrics are as follows: 1) Listenability: Is the lyric sounds natural with the melody? 2) Grammaticality: It the lyric grammatically correct? 3) Meaning: Is the lyric meaningful? 4) Quality: What is the overall quality of the lyric? The metrics to evaluate the melody are as follows: 1) Emotion [2]}: Does the melody represent the emotion of the lyrics? 2) Rhythm [3]}: Are the note durations and pauses of the melody sound natural? 3) Quality [1]}: What is the overall quality of the melody?
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